1. Field of Invention
The present invention relates to surface treatment methods, surface-treated substrates, methods of forming film patterns, etc. More particularly, the invention relates to a surface treatment method to obtain a substrate which is suitable to form conductive wiring films used for electrodes, antennas, electronic circuits, integrated circuits, etc., or to form film patterns, such as silicon film patterns, and which has desired uniform lyhophilicity; a surface-treated substrate obtained by the surface treatment; a method of forming a film pattern, etc.
2. Description of Related Art
In order to form wiring used for electronic circuits, integrated circuits, or the like, for example, photolithographic processes are used. In a related art lithographic process, a sensitized material, referred to as a resist, is applied onto a substrate which is preliminarily coated with a conductive film, a circuit pattern is exposed and developed, and the conductive film is etched following the resist pattern to form wiring. The lithographic process requires large-scale equipment, such as vacuum devices, and complex steps. In the lithographic process, only a small percentage of the material is used, and most of the material needs to be disposed of, resulting in an increase in production cost.
In contrast, U.S. Pat. No. 5,132,248 discloses a method in which a liquid in which conductive fine particles are dispersed is pattern deposited directly onto a substrate by an ink-jet process, and the deposited material is formed into a conductive film pattern by heat treatment or laser irradiation. In such a method, photolithography is not required, the process is greatly simplified, and the amount of raw material used is decreased.
However, in order to use the deposited material as wiring, the conductive fine particles must be overlapped with each other to a certain extent to form a thick film. That is, unless the conductive fine particles are overlapped with each other, portions in which the conductive fine particles are not brought into contact with each other may cause disconnections, etc. If the film pattern has an insufficient thickness, the electrical resistance is increased, and the resulting wiring has poor conductivity.
In the method of directly pattern depositing a liquid in which conductive fine particles are dispersed onto a substrate by an ink-jet process, since the liquid in which conductive fine particles are dispersed is used, the amount of the conductive fine particles deposited is limited in view of viscosity during discharge, etc., when a certain amount of liquid is discharged. On the other band, if an attempt is made to discharge a large amount of liquid at one time, it becomes difficult to control the formation position of wiring and the wiring width increases, thus being unsuitable for integration of electronic circuits, etc.
In order to properly form a conductive wiring film by the ink-jet process, Japanese Unexamined Patent Application Publication No. 59-75205 discloses a method in which the positions of ejected droplets are controlled by placing banks (walls). By using the banks, even if a certain amount of liquid is discharged, the droplets discharged onto the substrate remain between the spaces between the banks, and it is possible to form lines with a line width of approximately 30 μm with a positional accuracy of approximately 1 μm.
However, such banks must be formed by a photolithographic process, resulting in an increase in the cost.
Another method is also disclosed in which a pattern of lyophobic regions and lyophilic regions is preliminarily formed on a substrate, and a liquid material is selectively discharged onto the lyophilic regions by the ink-jet process. In such a case, since the liquid in which conductive fine particles are dispersed easily accumulates in the lyophilic regions, it is possible to form lines while maintaining the positional accuracy without forming banks.
However, this method requires the forming of the pattern for the lyophilic regions and the lyophobic regions using a mask, etc., and also requires the placing of alignment marks in order to deposit the liquid accurately on the lyophilic pattern, resulting in a complex process.
Since wet droplets spread because of the discharge onto the lyophilic regions, it is difficult to form thick conductive films. In order to increase the thickness, the number of times to discharge may be increased. However, unless the lyophobicity of the lyophobic region to the liquid is considerably increased, it is difficult to confine the liquid within the lyophilic region. Furthermore, the line width of the wiring formed is limited by the width of the lyophilic region of the substrate.
In order to form a silicon thin film pattern used for integrated circuits and thin-film transistors, in general, after an amorphous or polysilicon film is formed over the entire surface of a substrate by thermal CVD, plasma CVD, photo-assisted CVD, or the like, unwanted portions of the silicon film are removed by photolithography.
However, in the formation process of the silicon thin film pattern using CVD and photolithography, further enhancements are desired for the reasons described below.
Since the vapor phase reaction is used and silicon particles are generated in the vapor phase, the production yield is decreased due to the contamination of the apparatus and generation of foreign matter.
Since the gaseous material is used, it is difficult to obtain a film with a uniform thickness on a substrate whose surface is irregular.
Since the formation rate of the film is slow, productivity is low.
In plasma CVD, complex and expensive high-frequency generators, vacuum devices, etc., are required.
In photolithography, the process is complex, the utilization ratio of the material is low, and a large amount of waste, such as resists and etchants, is generated.
In terms of materials, since toxic and highly reactive gaseous silicon hydride is used, handling is difficult, and sealed vacuum devices are required because it is gaseous. In general, such devices are large-scale and the devices themselves are expensive, and also a large amount of energy is consumed in the vacuum system and the plasma system, resulting in an increase in the production cost.
In contrast, another method is also disclosed in which a pattern of lyophobic regions and lyophilic regions is preliminarily formed on a substrate, a liquid material containing an organic silicon compound is selectively discharged only onto the lyophilic regions by an ink-jet process, and the deposited material is transformed into a silicon film pattern by heat treatment or the like. Thereby, a silicon film pattern is formed accurately by a simple process.
As described above, an attempt has been made to form a film pattern by discharging a liquid containing conductive fine particles or a component, such as an organic silicon compound, to form the film as droplets onto a substrate in which lyophilicity or lyophobicity is adjusted uniformly or a substrate provided with a pattern of lyophobic regions and lyophilic regions.
In such a case, related art examples of the lyophobic treatment include a process of forming a lyophobic monomolecular layer, such as a self-assembled layer composed of organic molecules, on the surface of the substrate, a process of forming a fluorinated polymer layer on the surface of the substrate, and plasma treatment using a fluorocarbon compound as a reactant gas.
On the other hand, related art examples of the lyophilic treatment include ultraviolet irradiation and plasma treatment using oxygen as a reactant gas.